The long-range objective of our research is to develop an understading of the physiological and psychological aspects of pain perception, in order that we may provide improved treatment for patients with chronic pain. We pln to study neurophysiological and psychophysical mechanisms of pain perception. The neurophysiological research is aimed at the study of primary afferent nociceptive units in peripheral nerves, with the objectives of 1) determining the peripheral neural coding michanisms for thermal and mechanical pain perception, 2) determining the peripheral neural mechanisms for hyperalgesia induced by cutaneous injury, and 3) determining the effects of different therapeutic modalities on the activity and responses of primary afferent nociceptive units. The psychophysical research has the objectives of 1) understanding how normal subjects and different types of patients perceive their pan, by studying their response to experimental pain, and 2) obtaining a measure of the analgesic potency of various therapeutic modalities in patients with chronic pain.